Innovative Solutions for Energy Transitions of Small Islands: The Case of a Hybrid Photovoltaic System at the ENEA Climatic Observatory in Lampedusa Island

The decarbonization of energy-isolated systems is under investigation with a number of extensive national and international researches, including non-interconnected islands i.e. those islands whose electricity distribution network is not connected to the transmission system of the mainland. In the framework of the Italian Electricity System Research Plan, innovative technologies and solutions have been identified, projected, and tested aimed at reducing and optimizing the energy consumption of individual users in small islands, increasing the penetration of renewables, with a consequent reduction in climate-changing emissions. Focusing on the production of household hot water (40-50 ^% of electricity consumption for the end-user), research activities involved the experimental hybrid photovoltaic system installed at the ENEA Research Centre on Lampedusa island in the Mediterranean Sea, equipped with heat pump and thermal/electric storages. They include both modelling, using Matlab/Simulink to simulate stand-alone and grid-connected configurations, and experimental tests performed considering the load shifting during the hours of highest PV production in representative winter and summer weeks. On these bases, a technical-economic analysis was carried out for different configurations of the hybrid system, by applying standard and real load profiles; simulations were extended to an entire year varying PV system size (370–1480 W) and storage technologies (lead, lithium, and supercapacitors). In the stand-alone configuration, results show an energy advantage from supercapacitors and lithium storage as they are able to guarantee a 100 ^% comfort condition for different consumptions, including the real profile; setting a capacity of 2.4 kWh, supercapacitors lead to +4% in the Net Present Value and -0.3 years for the Discounted Payback Time compared to the other two electrical storage systems. For grid-connected configurations Discounted Payback Time decreases, energy self-sufficiency for hot water supply reaches such as 90%, and a PV self-consumption coefficient around 100 ^% in the case of 740 W p PV power with a supercapacitor system. Simulations were carried out even setting the absence of any electrical storage, showing that the self-sufficiency of the system is limited to 80%, with an optimal PV power value of 740 W p .